Two new complexes of bismuth nitrate with phthalic acid (H2phth) were synthesized by liquid state reaction. The complexes were characterized by chemical and elemental analyses, Fourier transformed infrared spectra, X-ray powder diffraction and thermgravimetry analysis. Their compositions are Bi(phth)(NO3)·4H2O and Bi(phth)(L-cys)0.5·H2O (L-H2cys = L-cystine), respectively. The crystal structure of the complexes belongs to monoclinic system with lattice parameters of a = 1.0792 nm, b = 2.2169 nm, c = 1.0306 nm and β = 95.68° for Bi(phth)(NO3)·4H2O; and a = 1.4183 nm, b = 2.2633 nm, c = 1.3753 nm and β = 96.49° for Bi(phth)(L-cys)0.5·H2O, respectively. IR spectra indicate that the bismuth(III) ion in the two complexes is six-coordinated by the carboxyl oxygen atoms from the ligands and oxygen atoms from nitrate ion, respectively. The thermal decomposition processes of the complexes under nitrogen include dehydration and pyrolysis of the ligands, and the final residue at about 480 °C is bismuthous oxide.